A novel method to directly quantify nanoparticles (NPs) in a soil matrix by laser ablation single particle inductively coupled plasma mass spectrometry (LA-sp-ICPMS) was developed. Different concentrations of 60, 100, or 250 nm diameter gold NPs (AuNP) were deposited directly on polyether sulfone (PES) ultrafiltration membranes or immersed in soil. The ICPMS sensitivity was calibrated using aqueous dissolved Au standards and an aqueous AuNP size standard dispersion was used to calculate the transmission efficiency. In the case of the soil samples, sizing proved to be more accurate when calibration occurred while ablating a non-spiked soil. A linear relation was found between the spiked AuNP number concentrations and the particle event frequencies measured in the ablated area. Particle recovery on PES filters ranged only between 29 to 42% and recovery of soil-spiked AuNP on thin tape was between 15 and 60% and increased with size. However, 70–85% mass recovery in the ablated area was obtained when the soil sample was deposited on a thicker, opaque double sided tape suggesting that the substrate material is instrumental in absorbing excess laser energy thus enhancing recovery. The rate of soil ablation and mass transfer into the plasma was quantified to calculate the recovery using the same soils spiked with indium. The presented method thus has significant potential to be used for routine quantification of the particle size distributions of engineered or natural NPs in soil and possibly other powder samples with significantly fewer artifacts than extraction followed by aqueous analysis.

中文翻译：

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激光烧蚀单颗粒ICPMS测定掺入土壤的金纳米颗粒的数量浓度和尺寸

开发了一种通过激光烧蚀单颗粒电感耦合等离子体质谱法（LA-sp-ICPMS）直接定量土壤基质中纳米颗粒（NPs）的新方法。将不同浓度的60、100或250 nm直径的金纳米颗粒（AuNP）直接沉积在聚醚砜（PES）超滤膜上或浸入土壤中。ICPMS灵敏度使用溶解的Au水溶液进行校准，并使用AuNP尺寸的水分散液计算传输效率。对于土壤样品，在消融未加尖的土壤时进行校准时，定径被证明是更准确的。发现加标的AuNP数浓度与在烧蚀区域中测得的颗粒事件频率之间存在线性关系。PES过滤器上的颗粒回收率仅在29％到42％之间，细带上掺加土壤的AuNP的回收率在15％到60％之间，并且随着尺寸的增加而增加。但是，当土壤样品沉积在较厚，不透明的双面胶带上时，在烧蚀区域的质量回收率为70-85％，这表明基体材料有助于吸收多余的激光能量，从而提高了回收率。使用掺有铟的相同土壤对土壤的消融速率和向血浆中的质量转移进行定量，以计算回收率。因此，所提出的方法具有很大的潜力，可用于常规定量工程化或天然NP在土壤以及可能还有其他伪像中的提取量少于水相分析后的其他粉末样品中的粒径分布。